They use anaerobic (without oxygen) digesters. Automatic scrapers send the manure from dairy barns to the methane digesters that are sunk into the ground.
Each digester holds three weeks of manure and is treated with bacteria found in the stomach of a cow. The tank is heated and cooks the manure. The methane produced is piped away to fuel generators or flows directly to the local gas utility pipeline.
What remains is separated into liquid and something like peat moss mulch. The mulch is used as bedding for the cows instead of sawdust, saving the farmers, for example, $50,000 a year. The sawdust "was like gold,"
So instead of poor dairy farmers, we have the story of a sustainable, recycling, methane-producing, prosperous dairy farmers.